1. Field of the Invention
This invention relates to a process for the conversion of carbohydrates to hydrocarbons, and more particularly to the conversion of sugars in the presence of a specified crystalline silicate zeolite catalyst.
2. Description of the Prior Art
There is a national interest in finding alternate sources other than petroleum for the production of liquid fuels and chemicals. U.S. Pat. No. 4,313,011, for example, has proposed the recovery of hydrocarbon fuels and chemical feedstocks by thermal conversion of plant biomass in a reducing atmosphere at temperatures of 200.degree. C. to 1000.degree. C. A summary of various processes for conversion of plant materials, including anaerobic digestion, fermentation, gasification and pyrolysis, appears in the publication by Anderson and Tillman entitled "Fuels from Waste", Academic Press, New York, 1977. Catalytic processes also have been developed. U.S. Pat. No. 4,300,009 discloses the conversion of plant or animal anabolites to liquid hydrocarbons in the presence of a crystalline aluminosilicate zeolite catalyst. The anabolites which are converted are characterized by an effective hydrogen to carbon ratio (H/C).sub.eff of less than 1 and are stated to be unsuitable since they give only low yields of premium fuels and chemicals and cause rapid loss of catalytic activity. U.S. Pat. No. 4,300,009 further points out that while it has been suggested to pyrolyze such materials to lower molecular weight product, such processes suffer the disadvantage of requiring substantial energy input. Other catalytic non-hydrocarbon processes include the conversion of alcohols to olefinic hydrocarbons as described in U.S. Pat. No. 4,148,835; the conversion of lower alcohols and their ethers, such as methanol and dimethyl ether, to a hydrocarbon mixture of ethylene, propylene and mononuclear aromatics as described in U.S. Pat. No. 3,979,472; and the catalytic conversion of mercaptans, sulfides, halides, amines and carbonyl compounds as described in U.S. Pat. No. 4,046,825. In U.S. Pat. No. 3,998,898, mixtures of difficult to convert oxygenates with easy to convert oxygenates such as alcohols, ethers, esters, long chain aldehydes and ketones are co-processed over a crystalline zeolite catalyst to provide aromatic products of gasoline boiling range. Among the compounds that are stated to be difficult to convert are included carboxylic acids and anhydrides, carbohydrates such as starch and sugars, lower glycols, glycerin, and other polyols and short chain aldehydes.